English

Özet

The data set contained 2181 normal lactation records of Friesian cows kept at Sakha Experimental Farm, Kafer El- Sheikh Government, belonging to Animal Production Research Institute, Ministry of Agriculture, Dokki, Cairo, Egypt were used to construct several selection indexes by using two relative economic values, actual relative economic value (REV₁) and one phenotypic standard deviation (REV₂). Variables studied were 305 day milk yield (305 d MY), 305 day fat yield (305 d FY) and 305 day Protein yield (305 d PY). Data were analysis by using MTDFREMAL Software.  The model include the main effects of month and year of calving, parity and days open as covariate and random effects of animals, permanent environmental and errors.

The estimated means and standard deviations for 305 d MY, 305 d FY and 305 d PY were 2806 ±949  kg , 102 ±37 kg and 79 ±28 kg, respectively; and their estimated heritabilities 0.29±0.01, 0.24±0.02 and 0.29±0.02, respectively. Repeatability estimates were 0.37±0.05, 0.44±0.06 and 0.51±0.06 for 305 d MY, 305 d FY and 305 d PY, respectively. Phenotypic, genetic environmental correlations among different variables were positive and significant.  Comparison of the two methods for estimating relative economic values explained no changes in any of the two methods for the expected genetic gain per generation for each variable. Our results indicate that, the two methods were succeeded in predicting the genetic progress per generation for the three variables studied. However, the second method (one phenotypic standard deviation) was recommended based on ease of estimation.